Ram for metal can shaper

ABSTRACT

An apparatus for forming a two-piece can comprising: a cylindrical housing, the cylindrical housing having a first end and a second end; a first round bushing having a longitudinal rectangular bore and received in the first end; a second round bushing having a longitudinal rectangular bore and received in the second end; a substantially rectangular ram which slides in the longitudinal rectangular bore of the first round bushing and the longitudinal rectangular bore of the second round bushing; a spring interposed between the first round bushing and the second round bushing and surrounding the substantially rectangular ram.

The present invention is in relation to the machines used to form or“neck” the end of the can cylinder as part of a two piece can process.

Beverages are commonly served in aluminum and metal cans which are madeat the pace of more than one million per day. They are generally formedfrom two pieces: a top (which generally has a tab for opening thebeverage) which is generally affixed to a bottom after it is filled witha liquid substance such as a beer or soda. It is desirable to make thecan as thin as possible, to reduce material and shipping costs. However,the can itself has to be strong enough to withstand both internal andexternal pressures. To do so the cylinder section of the can has manycurves in its top and bottom to make the can more rigid and able towithstand the internal and external pressures created by internal gasesand external axel loads created by stacking and handling. Necking downthe top of the container requires less metal to form the top, furtherreducing the cost of the container and the expense to the end user.

There are many steps in forming or pulling the metal used in making acan of very thin metal—most commonly aluminum. The can starts as a sheetof metal that is stamped into a cup shape. The cup shape then goes to abody maker where it is pulled into a cylinder shape with the tapereddomed bottom. From there it is then decorated with a design and thensent through an oven to cure the inks. A coating is then applied to theinside of the can. At this point the top of the cylinder is straight andround. It is at this point the top of the cylinder is then “necked down”to a smaller opening through a series of dies and pushers. These diesand pushers are held by a series of rams and cylinders that are attachedto a turret, or carrier. Both cylinders oppose each other and the ramsmove in opposing directions at the same speed as the turrets turnpushing the can under pressure into the dies through numerous stations.The required shape is then formed. This process is commonly referred toas “necking” the cans. Also the cylinder and ram assemblies are referredas “necker cylinders”.

The necker cylinders have many various components. The key componentsare the cylinder “bushing” and the ram or piston. The bushing and theram, combined are currently a liquid tight cylinder with seals atopposing ends to prevent lubricant leaks while the piston moves back andforth at high speeds during the necking process. The piston is a roundcylinder that rides in a brass or steel bushing. One end of the pistonhas two wheels that follow a rail on a stationary cam that has a curvein the rail track to make the piston move back and forth as the turretturns. To prevent the round piston from spinning in the bushing, thereis an internal key and keyway that also allows the cam followers to stayindexed to the rail of the cam and prevents centrifugal force fromturning the piston during high speed operation.

These old style ram assemblies are lubricated by hand in a very timeconsuming process that required regular line shut down time to assurethe pistons are properly lubricated. Newer machines have automatic orcontinuous lubrication to the ram assemblies by the means of greasetubes to each ram. This tube lubing process has continual problemsbecause the tubes are connected to special couplings to accommodate thespinning of the turrets. These couplings wear out and allow grease tocontaminate thousands of cans before the problem is detected. Oncedetected the line must be shut down for long durations until the problemis located among the many rams and then repaired. Another problem is theoil seals at the end of the bushings. These oil seals wear out and causecontamination as well and the shut down time is even greater. Hundredsof cylinders must be inspected to locate the problem. It must then beremoved and replaced with a rebuilt assembly.

The internal key and key way is also problematic. They often break downor loosen, destroying the ram assembly and commonly the oil seals aswell. Production is again interrupted and damage to the cam and themachine must be repaired.

These machines typically produce 2500 cans per minute. It is notuncommon for the machines to malfunction for 15 to 20 minutes beforeproduction can be halted. When a cylinder malfunctions the cans arecontaminated and must be scrapped. The shut down time to repair thesecylinders costs manufacturers $10,000 or more per hour in lost revenues.Most facilities maintain a complete extra set of these cylinders whichare being rebuilt and made ready for change-over either monthly orquarterly for every machine. This is a very time consuming process andvery costly as well due to the 8 to 16 hours required to replace thesecylinders. These shut downs cost on average more than $100,000.00 eachtime in loss of production plus the cost of rebuilding. The weight isanother inherent problem. These cylinder assemblies can weigh in excessof 20 pounds each requiring a tremendous amount of energy to turn theturrets due to the fact that the assemblies are made of brass and steel.

Numerous attempts have been made to try and solve these problems withinthe art. One design is the square ram assembly, which tries to eliminatethe lubrication problems and key way and weight as well. This designuses a rectangular ram and a solid bushing with a rectangular opening toaccept the ram. Both made of aluminum to address the weight issue and byapplying a Teflon-ceramic coating on the friction surfaces to addressthe lubrication problem. This solution only works for a short period oftime before the coating breaks down and fails requiring rebuild. Alsothe tooling adaptors are added to the ram because it is made of softaluminum which breaks and wears rapidly. This only increases the numberof assembly parts and cost of such parts. The rectangular ram doesaddress the key way issue but the points in the corners cause pinchpoints and wear edges as well. This only creates another inherentproblem or break down starting point, thus not a solid solution.

Accordingly, it is the object of the present invention to provide alubricant free assembly, with increased life span, less drag and lessfriction.

These and other features, aspects and advantages of the presentinvention will become better understood with reference to the followingdescription and claims.

SUMMARY OF THE INVENTION

The present invention relates generally to ram assemblies, and inparticular to a lubricant-free, low drag, low friction ram assembly withincreased life span.

According to one embodiment, an apparatus for forming a two-piece can isprovided, the apparatus comprising: a cylindrical housing, thecylindrical housing having a first end and a second end; a first roundbushing having a longitudinal rectangular bore and received in the firstend; a second round bushing having a longitudinal rectangular bore andreceived in the second end; a substantially rectangular ram which slidesin the longitudinal rectangular bore of the first round bushing and thelongitudinal rectangular bore of the second round bushing; a springinterposed between the first round bushing and the second round bushingand surrounding the substantially rectangular ram.

According to another embodiment, an apparatus for forming a two-piececan is provided, the apparatus comprising: a cylindrical housing, thecylindrical housing having a first end and a second end; a first roundbushing having a longitudinal rectangular bore and received in the firstend; a second round bushing having a longitudinal rectangular bore andreceived in the second end; a cylindrical cavity formed between thefirst round bushing and the second round bushing and surrounded by thecylindrical housing; a cornerless substantially rectangular ram whichslides in the longitudinal rectangular bore of the first round bushing,the longitudinal rectangular bore of the second round bushing and thecylindrical cavity; a spring in the cylindrical cavity and between thefirst round bushing and the second round bushing and surrounding thesubstantially rectangular ram; and a retaining means in communicationwith the spring for maintaining the spring in a portion of thecylindrical cavity.

These and other features, aspects and advantages of the presentinvention will become better understood with reference to the followingdescription and claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a prior art ram assembly;

FIG. 2 is a prior art ram assembly;

FIG. 3 depicts the present invention;

FIG. 4 depicts the present invention;

FIG. 5 depicts the present invention; and

FIG. 6 depicts the present invention.

DETAILED DESCRIPTION OF THE INVENTION

The following detailed description is of the best currently contemplatedmodes of carrying out the invention. The description is not to be takenin a limiting sense, but is made merely for the purpose of illustratingthe general principles of the invention, since the scope of theinvention is best defined by the appended claims.

FIG. 1 depicts a typical ram assembly 61. The bushing 62 has a roundbore 63 in which the ram slides in. The ram 64 has a key 65 that slidesin a key way (not shown) The tail portion 66 has two cam followers (67 aand 67 b). FIG. 2 depicts a cross sectional view of a portion of aBELVAC metal can forming machine. A central shaft 50 is motor driven androtates. The turrets 51 and 51 b are fix to the shaft and rotates withit. Series of rams are mounted to the turrets 51. A series oflubrication tubes 55 leads to a lubrication nozzles 56. The ram assembly54 includes a fixed bushing 57 having a round bore and a ram 58. Thetail portion 59 of the ram 58 carries two cam followers 59 a 59 b. Thecam followers 59 a an 59 b are mounted to ride on the sides of the fixedcam 60 which is an elongated protrusion forming a circle.

FIGS. 3-6 depict a ram assembly according to the present invention. Asshown the apparatus has: a cylindrical housing (112), cylindricalhousing having a first end (128) and a second end (130); a first roundbushing (115 b) having a longitudinal rectangular bore (138) andreceived in the first end (128); a second round bushing (115 a) having alongitudinal rectangular bore (140) and received in the second end(130); a substantially rectangular ram (111) which slides in thelongitudinal rectangular bore (138) of the first round bushing (115 b)and the longitudinal rectangular bore (140) of the second round bushing(115 a); a spring (119) interposed between the first round bushing (115b) and the second round bushing (115 a) and surrounding thesubstantially rectangular ram (111). The cylindrical housing (112) holdstwo solid bearings or bushings (115 a and 115 b) made of compositematerial and does not require lubricant between the ram and the bearinge.g.; “phenolic”. The housing is designed so that the bushings as wellas the spring assembly may be replaced. There may also be an integralattachment means (e.g. 140, 142) along the outside of at least one offirst end (128) and the second end (130). The first round bushing (115b) may be attached to the inside of the first end (128) of thecylindrical housing 112. It may be mechanically attached (screwed in),attached by an adhesive, such as Green Loctite™, or any other attachmentmeans. Green Loctite™ is an extremely low viscosity compound that isused to “fit” a shaft to a bearing. Since the compound has such lowviscosity, capillary action wicks the solution between the shaft and theinner race of the bearing. After a period of time (approximately 15minutes), the adhesive cements itself under an anaerobic reaction. Thesecond round bushing (115 a) may be attached in a similar manner,typically being slightly smaller than the inside of the cylindricalhousing and fitting snugly therein. As shown in FIG. 5, the integralattachment means is a threaded flange for attaching the apparatus to theassembly.

One of the intended advantages of the present invention is to reducedrag and friction at all points in the assembly. This is accomplishedthrough a number of different ways. The assembly having a first roundbushing (115 b) and a second round bushing (115 a) with a cylindricalcavity (150) between reduces the drag on the substantially rectangularram by providing less contact. Another way in which the drag is reduced,is by shaving off the four corners of the substantially rectangular ram,to make an octagonal ram (111), as shown in FIG. 6. It should beunderstood that because the corners are removed, there is much lesscontact and therefore much less drag and wear and tear on the ram. Whilethe ram (111) is referred to as octagonal, it should be understood thatit is still substantially rectangular, as can be seen in FIG. 6, becausevery small corners have been removed. The corners may also just beslightly rounded, or “chamfered”, resulting in a cornerless rectangularshape (not technically an octagon). Rounded corners would eliminatecorner pinching and wear point edges. Neither the steel ram nor thebushing require any type of coating or lubricant. This design keeps thecam followers indexed to the cam during rotation of the turret/carrierto counteract centrifugal force. It also eliminates the need for a keyand key way.

There may be a common groove (118) formed in the substantiallyrectangular ram (111). This may be particularly useful to receive aretaining means, such as a retaining clip (117). The retaining means(117) would, according to a preferred embodiment, surround at least aportion of the substantially rectangular ram (111) may secure a washer(116 b in FIG. 4 and 116 a in FIG. 5) and be in communication with thespring. This is an extremely valuable aspect of the present invention,because it can effectively double the life span of the apparatus. Thespring assembly charges the ram bi-directionally, so that the camfollowers will ride and wear only one side of the rail at a timedepending on which way the ram is charged. The opening in the outerhousing allows the operator to change the position the spring retainerthus changing the charge direction. This will double the life of the camand allows the use of only one cam follower which provides continuouscontact between the cam follower and the cam. This prevents creasingduring the metal forming process known as “necking” caused by back lashbetween the cam and the cam follower.

The steel ram may be charged bi-directionally to permit the use of asingle cam follower depending on the position of the retaining clip inthe common grove (118) in the ram (111). For example, FIG. 4 shows thespring (119) on the right side and a spring charge direction (160). FIG.5 shows the spring (119) moved to the left side and a spring chargedirection (162). The retaining clip (117) may be removed throughcylindrical cavity (170) in a top portion of the generally cylindricalhousing (110) and the spring (119) moved from side to side. The opening(170) as shown is a small opening in the center. There may also be anopening that runs the entire length of the cylindrical housing (110) andis parallel to the ram (111). This may provide would provide easymaintenance and would not depart from the opening as claimed.

The present invention provides many novel components in the ramassembly. The separate outer housing (110) made of light weight alloy,e.g., aluminum, is reusable time and time again and adapts to the commoncarrier or turret. The housing (110) also allows for the use of tworeplaceable non lubricated or coated bushings as well as the replaceablespring (119) assembly and allows operator to change the direction of thespring charge on the piston easily via the opening (170) in the top ofthe housing (110). The opening (170) in the housing (110) also allowsthe tool and dies to breathe during motion. The bushings (e.g. 115 a and115 b) are made of a long lasting durable material such as lien phenolor high comp and match well with a polished steel ram for long life.These materials are proven in use in a similar application in canproduction line and the bushing and the steel shaft needed not bereplaced after years of running without any type of lubrication. Someare still in operation since 1995. The bushings (e.g. 115 a and 115 b)are also replaceable together or individually when wear does occur andalso act as retaining surface for the spring (119) assembly to pushagainst as a leverage surface. Using two individual bushings (e.g. 115 aand 115 b) at each end of the outer housing allows much greaterprecision in the tolerances in machining the opening due to the shallowdepth of the bushing unlike the solid deep one piece bushing. Thisprovides more concentricity of all the parts moving along the invisibleaxis of the ram assembly there for providing consistency in the neckingprocess. Plus the bushings are light weight and much smaller than solidone piece bushing bodies currently in used today.

The novel spring assembly allows the steel ram to be chargebi-directionally to permit the use of a signal cam follower depending onthe position or the retaining clip in the common grove in the ram. Withthis constant contact between the cam follower and the cam provided bythe springs charge prevents creasing in the necking of the can. Thespring assembly also allows the use of one side of the cam rail at atime there for doubling the life of the cam and less rejects fromcreasing.

The ram is novel by its unique geometry, an octagon, which is elongatedon four sides to prevent corner pinching and wear edges found in squarerams. The ram also has a common grove in it for a spring retaining clipthat allows the ram to be charged and only require one cam follower tomove back and forth. The ram is made of a durable alloy steel andaccepts the current tooling used in the industry today. The ram is muchsmaller in size so there for much lighter than the typical round ramused today. The ram's unique geometry also provides indexing for the camfollower and eliminates the need for a key and key way to preventrotation caused by centrifugal force. Also the unique geometry providesfour surface to surface friction points between the ram and the bushingunlike a square or rectangle that have eight, four sides and fourcorners or points that make contact.

It should be understood that the foregoing relates to preferredembodiments of the invention and that modifications may be made withoutdeparting from the spirit and scope of the invention as set forth in thefollowing claims.

1. An apparatus for forming a two-piece can, said apparatus comprising:a cylindrical housing, said cylindrical housing having a first end and asecond end; a first round bushing having a longitudinal rectangular boreand received in said first end of said cylindrical housing; a secondround bushing having a longitudinal rectangular bore and received insaid second end of cylindrical housing; a substantially rectangular ramwhich slides in said longitudinal rectangular bore of said first roundbushing and said longitudinal rectangular bore of said second roundbushing; a spring interposed between said first round bushing and saidsecond round bushing and surrounding said substantially rectangular ram.2. An apparatus as in claim 1, further comprising at least one integralattachment means, wherein said integral attachment means is along theoutside of at least one of said first end and said second end.
 3. Anapparatus as in claim 1, wherein said substantially rectangular ram isan octagonal ram.
 4. An apparatus as in claim 1, further comprising acommon groove formed in said substantially rectangular ram.
 5. Anapparatus as in claim 1, further comprising an opening in a top portionof said generally cylindrical housing.
 6. An apparatus as in claim 1,further comprising at least one washer surrounding said substantiallyrectangular ram and in communication with said spring.
 7. An apparatusas in claim 1, further comprising at least one retaining meanssubstantially surrounding said substantially rectangular ram.
 8. Anapparatus as in claim 1, wherein at least one of said first roundbushing and said second round bushing is integrally formed from saidcylindrical housing.
 9. An apparatus as in claim 1, wherein each cornerof said substantially rectangular ram is removed to provide a cornerlesssubstantially rectangular ram.
 10. An apparatus for forming a two-piececan, said apparatus comprising: a cylindrical housing, said cylindricalhousing having a first end and a second end; a first round bushinghaving a longitudinal rectangular bore and received in said first end; asecond round bushing having a longitudinal rectangular bore and receivedin said second end; a cylindrical cavity formed between said first roundbushing and said second round bushing and surrounded by said cylindricalhousing; a cornerless substantially rectangular ram which slides in saidlongitudinal rectangular bore of said first round bushing, saidlongitudinal rectangular bore of said second round bushing and saidcylindrical cavity; a spring in said cylindrical cavity and between saidfirst round bushing and said second round bushing and surrounding saidsubstantially rectangular ram; and a retaining means in communicationwith said spring for maintaining said spring in a portion of saidcylindrical cavity.
 11. An apparatus as in claim 10, further comprisingat least one integral attachment means, wherein said integral attachmentmeans is along the outside of at least one of said first end and saidsecond end.
 12. An apparatus as in claim 10, wherein said substantiallyrectangular ram is an octagonal ram.
 13. An apparatus as in claim 1,further comprising a common groove formed in said substantiallyrectangular ram.
 14. An apparatus as in claim 1, further comprising anopening in a top portion of said generally cylindrical housing.
 15. Anapparatus as in claim 1, further comprising at least one washersurrounding said substantially rectangular ram and in communication withsaid spring.
 16. An apparatus as in claim 1, further comprising at leastone retaining means substantially surrounding said substantiallyrectangular ram.
 17. An apparatus as in claim 1, wherein at least one ofsaid first round bushing and said second round bushing is integrallyformed from said cylindrical housing.